Hydrocarbon streams produced from underground formations usually are mixtures of oil, gas and water. The produced oil, gas and water eventually must be separated. The industry is continually searching for more efficient and compact systems and improved methods for achieving separation.
In separating these components, a gas-liquid separation may be followed by a subsequent liquid-liquid separation. Liquid-liquid separation devices may be suitable for either water continuous or oil continuous flow regimes. A water continuous flow employs water as the continuous phase with oil droplets (dispersed phase) held in the water. Alternately, oil continuous flow refers to a stream in which oil serves as the continuous phase, with water droplets being held within the continuous oil phase.
United States Patent Application Publication US 2008/0087608 A1 to Wang et al. describes a method and apparatus for inline controlled water separation. Another publication discloses bulk separation of oil-water mixtures using liquid-liquid cylindrical cyclones. See Mathiravedu, R. S. et al., Performance and Control of Liquid-Liquid Cylindrical Cyclone Separators, Journal of Energy Resources Technology, volume 132, page 011011-1 (March 2010).
In conducting oil/water separation in the field there may be competing goals for separation of the liquid stream. That is, it usually a goal to produce a highly pure water stream to achieve regulatory requirements for disposal of water into the environment. At the same time, however, there may be a competing goal to produce an oil stream with the lowest possible amount of water that can be achieved. It has been observed that achieving one of such goals compromises the ability to achieve the other goal. This invention is directed to improved systems and methods for achieving separation of multiphase production streams.